This invention relates generally to turbomachines of the type having adjustable vane stages and, more particularly, to an improvement in support systems for vane operating unison rings.
In turbomachines, such as axial flow compressors, where stator or casing mounted vanes direct the flow of fluid impelled by rotor mounted blades, enhanced performance has been achieved by mounting the stator vanes for positional adjustment relative to the rotating blades. Typically, in adjustable vane arrangements each vane in a stage of adjustable vanes has a shaft rotatably supported on a casing of the turbomachine and each shaft has rigidly connected to it an actuating arm so that pivotal movement of the actuating arms effects concurrent rotation of the shafts and the attached vanes. Simultaneous pivotal movement of each of the actuating arms in a vane stage is typically effected by a unison ring disposed around the casing and connected to the actuating arms through bearings. In heretofore proposed systems for supporting unison rings relative to casings and for connecting unison rings to individual actuating arms, relatively complex and expensive structural combinations have been provided to effect support of the rings independently of the actuating arms. The purpose of such independent support is minimization of forces on the vane shafts which tend to tilt or cock the shafts in their mountings and thus increase the force level necessary for vane adjustment. A novel unison ring support system according to this invention embodies simplified and effective structure for supporting the unison ring on the turbomachine casing independently of the actuating arms and, thus, represents an improvement over other heretofore known systems.